<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            border:2px solid green;
            /* border-radius:25px; */
            border-top-left-radius: 50px;
            border-top-right-radius: 50px;
            border-bottom-left-radius: 20px;
            border-bottom-right-radius: 20px;

            width: 300px;
            height: 300px;
            } 
    </style>
</head>
<body>
    <div></div>
</body>
</html>